Fell running is a gruelling sport but it offers the best way to unlock the secrets of Cumbria's mountains, writes Richard Askwith

If you go out on the Borrowdale fells on Wednesday evening, you'll probably be looking for a bit of peace and quiet. You may be disappointed. By and large, the slopes of Great Crag and Watendlath are as tranquil as any in the Lake District: well loved by locals, but not famous enough to attract great crowds of walkers. This week, however, the people disturbing the tranquillity won't be walking. They'll be running.

If you go out on the Borrowdale fells on Wednesday evening, you'll probably be looking for a bit of peace and quiet. You may be disappointed. By and large, the slopes of Great Crag and Watendlath are as tranquil as any in the Lake District: well loved by locals, but not famous enough to attract great crowds of walkers. This week, however, the people disturbing the tranquillity won't be walking. They'll be running.

The precise nature of the disturbance - caused by the annual Langstrath Fell Race - will depend on where you hear it. If the runners are coming uphill from beneath you, the first sound to invade your consciousness is likely to be their breathing - desperate rasps for air like the honks of a cross goose. If they're coming down from above, you're more likely to notice the grumbling of loose stones beneath their feet, followed - suddenly - by violent grunts and thuds as they plummet suicidally past you.

Their faces are likely to be contorted with pain and concentration, their complexions various shades of scarlet, their legs splattered in mud and, in some cases, blood. Contemplating them - and reflecting on the fact that the fastest runners will complete the four-and-a-half-mile course, including 1,400ft of ascent and descent, in little more than half an hour - you are unlikely to feel much envy. Yet, as I contemplate them now from the comfort of my desk, envy is precisely what I feel. In fact, it's just possible that, come Wednesday, I shall head for the Lakes and join them. What better way to spend one of the last evenings of spring than to be honking and plummeting with them, rejoicing in the freedom of the mountains?

Fell-running is one of Britain's most marginal sports. As many as 5,000 people in Britain (including me) participate; but scarcely half that number do so regularly, and there are probably only a couple of hundred - mostly from Cumbria and Yorkshire - who do so well. As for what they do: the sport embraces a range of activities, from short dashes up and down a single slope (traditionally for cash prizes) to unstructured journeys of discovery lasting all day and more. What they have in common is a vision of mountains as obstacles that exist in order to be climbed and descended as fast as humanly possible.

Is this to miss the point of England's loveliest hills? On the contrary. After 15 years of doing it, most recently while researching a book on the subject, I have come to the conclusion that fell-running unlocks the secrets of such hills as no other mode of perambulation can.

There is, for a start, something about moving over mountains at reckless speed that forces you to engage more intimately with the terrain than you otherwise would. Running downhill, especially, means taking your life in your hands; so does running on exposed, unfamiliar hills in hostile conditions. Misread the lie of some loose stones, or lose your bearings in the course of some all-day foul-weather marathon, and the consequences can be catastrophic. Hence those grimaces of concentration.

Then there's the fact that, unlike walkers, runners aren't anchored to the road. If it takes you three hours to climb Skiddaw or Helvellyn, you need to head back for the car park pretty much the moment you reach the top. If it takes you 45 minutes (and next to no time coming down), you can afford to explore. Running, in other words, opens up to you whole tracts of mountain that would otherwise be beyond your reach. That's a great freedom - and a passport to some hauntingly unfrequented places. Run across the heathery wilderness at the back o'Skiddaw, for example, or the grassy, curved uplands between Steel Fell and the Langdales, and you can go for hours without spotting another human being. Yet they say that the Lake District is overcrowded.

I dwell on the Lakes because that is where I have done most of my fell-running. It's not the sport's only stronghold: others include Wales, Scotland, Northern Ireland, Yorkshire, Northumberland, Lancashire, Derbyshire, and Shropshire. But Cumbria is its heartland: the scene of more than 50 fell races a year, including most of the really tough, mountainous ones, and the repository of much of the sport's rich stock of legend.

That's another joy of fell-running: the fact that it reveals so many layers of otherwise invisible tradition. It gives shape, for example, to the Cumbrian calendar, with each small community rolling out in turn to support its own event, from the Ennerdale in June to Skiddaw in July, Borrrowdale and Grasmere at either end of August, the Three Shires in September, the Langdale Horseshoe in October, and so on.

It also gives depth to the landscape, which is steeped in the romance and history of the sport. If you didn't realise that you were in fell-running country you could, for example, look up from Grasmere at the looming, brackened roughness of Butter Crags and have no inkling that you were gazing at hallowed turf. Yet true Cumbrians know that this is where Ernest Dalzell used to electrify the crowds with his breakneck descents before the First World War, where Bill Teasdale defied the laws of physics and biology in the 1950s and 1960s, where Fred Reeves and Tommy Sedgwick fought their suicidal duels in the 1970s.

So it is with other slopes. Few views thrill the heart so infallibly as that of Wastwater gleaming, as you gaze down on it from any one of the arc of peaks above; but the thrill is all the greater if you can remind yourself that the surrounding mountains are those on which the indestructible Joss Naylor has lived, worked and run for the past 60 years or so. The satisfaction of struggling up Skiddaw gains a new piquancy if you pause to consider that Kenny Stuart, a gardener from nearby Threlkeld, once ran from central Keswick to the summit and back in two minutes over the hour. And who, toiling down the green slopes of Catbells, can be said to have exhausted that mountain's mysteries if they do not marvel at the thought that Gavin Bland, a Borrowdale shepherd, once ran from its summit to its base (at Stair village hall) in under five minutes?

To the uninitiated, such details may seem arcane. To me, they define Cumbria's appeal: a matchless landscape, made for adventure and inhabited by - among others - people whose heads are full of the lore of that landscape.

In fact, many modern Cumbrians know nothing of fell-running. I spent years running in the hills around Keswick before I found anywhere to stay where they regarded my muddy exploits with anything but genteel disapproval. In due course, however, I discovered a whole network of fell-runner-friendly establishments, and these are as good places as anywhere for outsiders who are interested in the sport to start feeling their way into it. They range from comfortable hotels (the Langstrath and the Scafell in Borrowdale both sponsor fell races) to friendly b&bs (Pete Richards, proprietor of Dunsford guesthouse in Keswick, is secretary of the local fell-running club, several of whose members also run guesthouses in and around the town), and even camping or caravan sites. (Tommy Sedgwick's, at Burton in Lonsdale on the Cumbria/Lancashire borders, offers dazzling views and the chance to shake hands with an all-time great). What they have in common - with each other and with the world of fell-running generally - is a sense of warm, welcoming community.

For a real sense of history, though, you might prefer to stay just south of Keswick in the Derwentwater Youth Hostel, where the great Bob Graham once lived. Graham was a guesthouse-keeper who in 1932 completed a 72-mile circuit of the mountains around Keswick - 42 peaks in all - in the space of 24 hours. Long-distance fell-runners have been aspiring to do the same ever since. It was nearly three decades before anyone succeeded; today, more than 1,200 people have done his "round" - including, eventually, me. The five years of obsessive training and reconnaissance that I had to put in first were among the most rewarding of my life, and cemented my love affair with the Lake District. By the time I succeeded, at the fourth attempt, I knew those 42 peaks better than my (neglected) back garden, as did my (neglected) family and friends.

It also left me with memories - sprinting down Blencathra by moonlight, or watching the sun burst out beneath me from the Helvellyn ridge at dawn - that still raise my spirits when I think of them. That's why, for me, Cumbria will always be fell-running country.

Sometimes I wonder what I used to see in those mountains, before I realised what they were really for.

'Feet in the Clouds' by Richard Askwith is published by Aurum Press (£16.99). Readers can order the book for the special price of £14.99 (inc p&p) by calling 01903 828503 and quoting AUR153